To meet the demand for wireless data traffic having increased since deployment of 4G communication systems, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’.
The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like.
In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
A wireless communication system using an unlicensed frequency band operates a corresponding radio access technology (RAT) in the unlicensed frequency band, rather than a licensed frequency band. Unlike the licensed frequency band, the unlicensed frequency band is free from cost and has a wide bandwidth. Accordingly, the unlicensed frequency band can enhance system capacity and per-user throughput with a low cost. The biggest technical issue of the wireless communication system using the unlicensed frequency band is coexistence with another RAT, for example, wireless local area network (WLAN), in the existing unlicensed frequency band.
The WLAN adopts carrier sense multiple access with collision avoidance (CSMA/CA). In particular, the WLAN transmits a signal based on listen-before-talk (LBT). Such a wireless communication system using the unlicensed frequency band long term evolution unlicensed (LTE-U) needs to coexist with the WLAN. For doing so, the wireless communication system using the unlicensed frequency band can transmit a signal based on the LBT like the WLAN.
The wireless communication system carries out communication on a subframe basis. The first few symbols of the subframe contain control information used for communication between a base station and a terminal. The base station and the terminal can communicate with each other by sharing the control information. Since a device supporting the wireless communication system gets a transmission opportunity at an arbitrary time, the base station of the wireless communication system waits for a start of the subframe, that is, a subframe boundary in order to transmit the control information. However, while the base station of the wireless communication system awaits the subframe boundary, a WLAN device can determine an idle channel and transmit a signal on the channel. In this case, the base station of the wireless communication system can lose the signal transmission opportunity.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.